Mozilla has delayed the delivery of Firefox 3.5 Release Candidate (RC) until late next week to take care of several last-minute bugs, a company executive said.

Last month, Mozilla had slated Firefox 3.5 RC to ship in the first week of June. “Even before shipping the RC, we've managed to find a number of issues that needed fixing,” said Mike Beltzner, the director of Firefox, in an e-mail reply to questions about Firefox 3.5 RC's status. “When I last looked, all but a few were complete, with fixes for the rest due imminently.”

According to meeting notes posted yesterday by Mozilla, there are 10 bugs still awaiting a fix before Firefox 3.5's code can be locked in preparation for a last round of internal testing before release.

Beltzner attributed the bug finds to a “newfound rigor” in testing, as well as a larger number of users hammering on the RC code. “[All this] makes it easier for us to spot potential problems with a milestone much earlier than ever before,” he said. Mozilla is now hoping to post Firefox 3.5 RC for download late next week, in the June 10-12 time frame.

The final version of Firefox 3.5 may yet make Mozilla's end-of-this-month deadline. But all things will have to go smoothly, and Mozilla would have to limit itself to a single RC.

Last year, Mozilla delivered the final release candidate of Firefox 3.0 on June 4, then launched the browser two weeks later, on June 17. Assuming it meets that same timeline this year, Mozilla could ship Firefox 3.5 by June 25 if it sticks to just one RC and drops that on users by June 12.

Firefox currently accounts for 22.5% of the browser market, according to Web metrics company Net Applications' most-recent data. But it faces renewed competition on almost every front, including Microsoft and its Internet Explorer 8, Google's Chrome browser, and even Opera Software, which launched a public beta of Opera 10 yesterday.

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